<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button id="btn">按钮</button>

    <script>

        function onClick(){
            console.log("按钮被点击了");
        }
        // capture选项都是false, 只有一个添加成功
        btn.addEventListener("click", onClick);
        btn.addEventListener("click", onClick);

        // capture选项都是true, 只有一个添加成功
        btn.addEventListener("click", onClick, {
            capture: true,
        });
        btn.addEventListener("click", onClick, {
            capture: true,
            once: true,
        });

    </script>
</body>
</html>